This research project is to provide information on the function of the epididymis and vas deferens, particularly with respect to maturational changes that occur in spermatozoa as they traverse the duct. Methods that will be used include: electron microscopic study of the structure of the epithelium and to transfer of materials from the blood to the lumen of the duct; biochemical study of the inter-relationships between the physiological compartments (lumen, epithelium, interstitium): and study of the properties of the plasma membrane of the sperm and how these properties change as the sperm migrates along the duct.